#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;

/**
 * @brief Prepares shell output variables for selection by specific menus (THP or DSY)
 * 
 * This function prepares all shell output variables to be selected by specific menus later.
 * It handles various material types and computes stresses, strains, and other output quantities.
 * 
 * 
 * @param CM Material properties array
 * @param STRS Stress array
 * @param IY Element connectivity array
 * @param INDEX Index array
 * @param ENSHEL Energy array for shells
 * @param SHEMAS Shell mass array
 * @param N Current element number
 * @param MTYP Material type
 * @param IETYP2 Element type array
 * @param AUX Auxiliary output array to be filled
 * @param LNSTR Layer number array
 * @param ROEL2 Rotational energy array
 * @param XNSMSH Non-structural mass array
 * @param SHTHK Shell thickness array
 * @param XMTSHL Mass matrix array
 * @param TEELE2DI Thermal energy array
 * @param XIMSCSH IMSC array
 */
void FM4N(const vector<double>& CM, vector<double>& STRS, const vector<vector<int>>& IY,
          const vector<int>& INDEX, const vector<vector<double>>& ENSHEL, const vector<double>& SHEMAS,
          int N, int MTYP, const vector<int>& IETYP2, vector<double>& AUX, const vector<vector<int>>& LNSTR,
          const vector<vector<double>>& ROEL2, const vector<double>& XNSMSH, const vector<double>& SHTHK,
          const vector<double>& XMTSHL, double TEELE2DI, const vector<double>& XIMSCSH) {

    // Constants from modules
    const int NVARS = 0; // Should be defined from MATELE_COM
    const int NDMG = 0;  // Should be defined from MATELE_COM
    const int ILGRNG = 0; // Should be defined from MATELE_COM
    const int ISHTHP = 0; // Should be defined from OUTPUT_COM
    const vector<int> MENUSH(30, 0); // Should be defined from OUTPUT_COM

    // Local constants
    const int NPAUXSH = 65;
    const double ONE = 1.0;
    const double RT3 = sqrt(3.0);
    const double FAC1 = 2.0 * RT3 / 12.0;

    // Local arrays
    vector<double> S1(48), S2(48), S3(48), S4(48), S5(48);
    vector<double> BS1(48), BS2(48), BS3(48);
    vector<double> BSMEM(3), SMEM(3), SMET(2);

    // Initialize AUX array
    fill(AUX.begin(), AUX.begin() + NPAUXSH + NVARS + NDMG + 2, 0.0);

    int IN = INDEX[N-1] - 1;
    int IGAUS = IETYP2[N-1];

    // Fully integrated BWC similar to HT for output
    if (IGAUS > 2) IGAUS = 1;

    double FACM = 0.25;
    if (IY[4][N-1] == 0) FACM = 1.0 / 3.0;

    int NMAT = IY[0][N-1];
    double SHMS = SHEMAS[N-1] / pow(ROEL2[0][N-1], 2);

    // Set specific output values based on menu selections
    if (MENUSH[19] != 0) AUX[38] = XNSMSH[N-1];  // NSMAS
    if (MENUSH[21] != 0) AUX[40] = XMTSHL[N-1];  // MSTRM
    if (MENUSH[23] != 0) AUX[44] = TEELE2DI;     // LSI
    if (MENUSH[28] != 0) AUX[45] = XIMSCSH[N-1]; // IMSC

    // Process based on material type
    switch (MTYP) {
        case 101: {
            // Material type 101 processing
            double THICK = STRS[IN];
            double THK = (IGAUS == 0 || IGAUS == 2) ? STRS[IN+14] : STRS[IN+36];
            if (IGAUS == 1) IN -= 5;

            double FAC = -0.083333333 * THK * THK * THK;
            AUX[0] = FAC * STRS[IN+11];
            AUX[1] = FAC * STRS[IN+12];
            AUX[2] = FAC * STRS[IN+13];
            AUX[5] = THK * STRS[IN+6];
            AUX[6] = THK * STRS[IN+7];
            AUX[7] = THK * STRS[IN+8];
            AUX[8] = THICK;

            // Lower/Upper/Membrane stress
            AUX[14] = STRS[IN+6] - 0.5 * THK * STRS[IN+11];
            AUX[15] = STRS[IN+7] - 0.5 * THK * STRS[IN+12];
            AUX[16] = STRS[IN+8] - 0.5 * THK * STRS[IN+13];
            AUX[17] = STRS[IN+6] + 0.5 * THK * STRS[IN+11];
            AUX[18] = STRS[IN+7] + 0.5 * THK * STRS[IN+12];
            AUX[19] = STRS[IN+8] + 0.5 * THK * STRS[IN+13];
            AUX[20] = STRS[IN+6];
            AUX[21] = STRS[IN+7];
            AUX[22] = STRS[IN+8];

            // Lower/Upper strains
            if (ISHTHP != 0) {
                int IND = (IGAUS == 1) ? IN + 36 : IN + 14;
                AUX[23] = STRS[IND+3];
                AUX[24] = STRS[IND+4];
                AUX[25] = 0.5 * STRS[IND+5];
                AUX[26] = STRS[IND];
                AUX[27] = STRS[IND+1];
                AUX[28] = 0.5 * STRS[IND+2];
                if (ILGRNG == 1) LOGSTRAIN(MTYP, AUX[23]);
            }

            // Energy calculations
            AUX[NPAUXSH + NVARS + NDMG] = FACM * ENSHEL[0][N-1] / SHMS;
            AUX[NPAUXSH + NVARS + NDMG + 1] = FACM * ENSHEL[1][N-1] / SHMS;
            return;
        }

        case 100: {
            // Simple case for material type 200
            AUX[8] = STRS[IN];
            return;
        }

        case 0: {
            // Eliminated element case
            return;
        }

        case 161: {
            // Thick shell element (type 460)
            AUX[3] = 0.0;
            AUX[4] = 0.0;

            double THK0 = STRS[IN];
            double THK = 0.25 * (STRS[IN+1] + STRS[IN+20] + STRS[IN+39] + STRS[IN+58]);

            // Stress components
            double SXX1 = STRS[IN+2], SYY1 = STRS[IN+3], SXY1 = STRS[IN+4];
            double SYZ1 = STRS[IN+5], SZX1 = STRS[IN+6], SZZ1 = STRS[IN+7];
            double SXX2 = STRS[IN+8], SYY2 = STRS[IN+9], SXY2 = STRS[IN+10];

            // Average and difference calculations
            double AVRGSXX = 0.5 * (SXX1 + SXX2);
            double AVRGSYY = 0.5 * (SYY1 + SYY2);
            double AVRGSXY = 0.5 * (SXY1 + SXY2);
            double DIFFSXX = 0.5 * (SXX2 - SXX1);
            double DIFFSYY = 0.5 * (SYY2 - SYY1);
            double DIFFSXY = 0.5 * (SXY2 - SXY1);

            // Strain calculations
            double AVGEPXX = 0.5 * (STRS[IN+11] + STRS[IN+17]);
            double AVGEPYY = 0.5 * (STRS[IN+12] + STRS[IN+18]);
            double AVGEPXY = 0.5 * (STRS[IN+13] + STRS[IN+19]);
            double DIFEPXX = 0.5 * (STRS[IN+17] - STRS[IN+11]);
            double DIFEPYY = 0.5 * (STRS[IN+18] - STRS[IN+12]);
            double DIFEPXY = 0.5 * (STRS[IN+19] - STRS[IN+13]);

            // Set output values
            AUX[0] = FAC1 * THK0 * THK0 * DIFFSXX;
            AUX[1] = FAC1 * THK0 * THK0 * DIFFSYY;
            AUX[2] = FAC1 * THK0 * THK0 * DIFFSXY;
            AUX[5] = THK0 * AVRGSXX;
            AUX[6] = THK0 * AVRGSYY;
            AUX[7] = THK0 * AVRGSXY;
            AUX[8] = THK;

            // Transverse stress and strain
            AUX[12] = SZZ1;
            AUX[13] = STRS[IN+16];

            // Lower/Upper/Membrane stress
            AUX[14] = AVRGSXX - RT3 * DIFFSXX;
            AUX[15] = AVRGSYY - RT3 * DIFFSYY;
            AUX[16] = AVRGSXY - RT3 * DIFFSXY;
            AUX[17] = AVRGSXX + RT3 * DIFFSXX;
            AUX[18] = AVRGSYY + RT3 * DIFFSYY;
            AUX[19] = AVRGSXY + RT3 * DIFFSXY;
            AUX[20] = AVRGSXX;
            AUX[21] = AVRGSYY;
            AUX[22] = AVRGSXY;

            // Lower/Upper strains
            AUX[23] = AVGEPXX - RT3 * DIFEPXX;
            AUX[24] = AVGEPYY - RT3 * DIFEPYY;
            AUX[25] = 0.5 * (AVGEPXY - RT3 * DIFEPXY);
            AUX[26] = AVGEPXX + RT3 * DIFEPXX;
            AUX[27] = AVGEPYY + RT3 * DIFEPYY;
            AUX[28] = 0.5 * (AVGEPXY + RT3 * DIFEPXY);

            // Energy calculations
            AUX[NPAUXSH + NVARS + NDMG] = FACM * ENSHEL[0][N-1] / SHMS;
            AUX[NPAUXSH + NVARS + NDMG + 1] = FACM * ENSHEL[1][N-1] / SHMS;
            return;
        }

        default: {
            // Handle other material types
            int ISLN1, ISTEP, ISFIX, IADD, IADD1, ITETA = 0, ISTRAIN = 0, IXCP = 0;

            if (IGAUS == 1) {
                // Fully integrated elements
                ISLN1 = LNSTR[0][NMAT-1];
                ISTEP = LNSTR[2][NMAT-1];
                ISFIX = 4 * ISLN1 + LNSTR[3][NMAT-1];

                }
            } else {
                // BT and BWC elements
                ISLN1 = LNSTR[0][NMAT-1];
                ISFIX = ISLN1 + LNSTR[1][NMAT-1];
                ISTEP = LNSTR[2][NMAT-1];

                }
            }

            // Continue with processing for other material types...
            // (Additional code would go here to handle the remaining cases)
        }
    }
}

// Helper function declarations (would need to be implemented)
void LOGSTRAIN(int MTYP, double& strain);
void BACKSTR(vector<double>& BS1, vector<double>& BS2, vector<double>& BS3, 
             const vector<double>& STRS, const vector<double>& STRS_DELTA, 
             int ISFIX, int ISTEP, int IP, int MTYP, const vector<double>& CM);
void HILLSG(const vector<double>& CM, const vector<double>& STRS_DELTA,
            vector<double>& S1, vector<double>& S2, vector<double>& S3,
            vector<double>& SMEM, int K1, int K2, double& VSIG1, double& VSIG2,
            double& VSIG3, vector<double>& BS1, vector<double>& BS2,
            vector<double>& BS3, vector<double>& BSMEM);
void HILL48(const vector<double>& CM, vector<double>& S1, vector<double>& S2,
            vector<double>& S3, vector<double>& S4, vector<double>& S5,
            vector<double>& SMEM, int K1, int K2, double& VSIG1, double& VSIG2,
            double& VSIG3, vector<double>& BS1, vector<double>& BS2,
            vector<double>& BS3, vector<double>& BSMEM, vector<double>& SMET,
            double XCP, double YCP);
void HILL90(const vector<double>& CM, const vector<double>& STRS_DELTA,
            vector<double>& S1, vector<double>& S2, vector<double>& S3,
            vector<double>& SMEM, int K1, int K2, double& VSIG1, double& VSIG2,
            double& VSIG3, vector<double>& BS1, vector<double>& BS2,
            vector<double>& BS3, vector<double>& BSMEM);
void BARLATSG(const vector<double>& CM, vector<double>& S1, vector<double>& S2,
              vector<double>& S3, vector<double>& S4, vector<double>& S5,
              double XCP, double YCP, vector<double>& SMEM, int K1, int K2,
              double& VSIG1, double& VSIG2, double& VSIG3, vector<double>& BS1,
              vector<double>& BS2, vector<double>& BS3, vector<double>& BSMEM,
              vector<double>& SMET);